1. Field of the Invention
The present invention relates to a liquid crystal projection display wherein a liquid crystal is thermally written with a laser beam.
2. Description of the Related Art
A demand for a large screen display has recently become great in control applications, particularly for such a display capable of displaying graphic patterns with high resolution. The liquid crystal projection display which uses a laser beam for thermal writing to the liquid crystal is a promising candidate meeting such requirements.
In the liquid crystal projection display, writing to the liquid crystal is achieved by deflecting a laser beam generated by a laser source with optical axis control means such as galvanometer mirrors and irradiating it onto the liquid crystal. Deflection of the laser beam is performed in the two directions of X axis and Y axis. As optical axis control means, a galvanometer type deflector or a rotary polygon mirror type deflector is employed which effects laser beam deflection by means of its mechanical displacement. In this case, however, the speed of displacement varies at the start and end of the mechanical displacement, and hence at the start and end of the deflection of the optical axis. As a result, there arises a problem that the width of a written line changes.
To solve this problem, it is known in the art that a laser beam for thermal writing is raster-scanned wider than the width of the liquid crystal to ensure a constant speed over the surface of the liquid crystal itself and a constant width of written lines. This technology is described in "Proceeding of the S.I.D.", Vol. 19/1, 1978, at pp.1 to 7.
With this technology, it is necessary for the optical axis controller to be mechanically displaced even to the outside of the writing surface of the liquid crystal, resulting in a disadvantage that the writing time becomes long.